Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$222.41	7.153%	$238.319	$238.32	$238.30	$238.30
Purchase #2	$150.63	7.649%	$162.1517	$162.15	$162.15	$162.20
Purchase #3	$80.64	6.763%	$86.0937	$86.09	$86.10	$86.10
Purchase #4	$149.70	5.803%	$158.3871	$158.39	$158.40	$158.40
Purchase #5	$145.90	6.356%	$155.1734	$155.17	$155.15	$155.20
Purchase #6	$169.59	5.466%	$178.8598	$178.86	$178.85	$178.90
Purchase #7	$74.65	10.249%	$82.3009	$82.30	$82.30	$82.30
7 purchase totals =	$993.52		$1,061.2856	$1,061.28	$1,061.25	$1,061.40